Advances in photovoltaic technology have helped solar energy gain mass appeal among those wishing to reduce their carbon footprint and decrease their monthly energy cost. However, the fabrication of solar cells, used to make solar panels, typically includes various processes that are time-consuming and involve expensive equipment, which can make it costly to mass-produce solar panels.
Fabricating solar cells can be made more efficient by processing many wafers simultaneously. In existing technology, during processing, for example during the deposition of material, a plurality of wafers are transferred into a processing chamber for material deposition using a carrier. The carrier may take the form of a graphite tray with separate compartments for each of the plurality of wafers. The wafers remain on the carrier throughout the processing steps. For example, when a chemical vapor deposition (CVD) step is carried out on the wafer, the carrier is present in the CVD chamber with the wafers.
While using a carrier in this manner has the advantage of being able to transfer many wafers between processing steps, it also has many disadvantages. For example, in order to process many wafers, large carriers are needed. Large carriers are expensive to manufacture, are more difficult to maneuver with a robot, and may damage the robot due to their weight. Further, because some processing steps involve heating the wafers, a great amount of heat energy is transferred to the large carriers. This thermal energy may dissipate in portions of the process where heat is not desirable and may damage equipment. Further, the current carriers are made of graphite which is fragile and prone to breaking. Breaking of carriers is not only costly due to replacement cost, which may be around $20K, but also because it increases production costs due to downtime and cleaning of equipment.
Because solar panel installations require very little post installation maintenance, the viability of these projects often turns on the projected rate of return derived from comparing the fixed value of the energy generated over the lifetime of the system versus the upfront costs of fabrication, and installation. In multi-megawatt projects, where power may be sold to the offtaker for less than $50 per megawatt hour, cost reductions of pennies per watt can be the difference between a project being viable or too expensive. Therefore, engineers are always seeking innovations to lower the cost of fabrication of solar cells without sacrificing speed of manufacture or efficiency of the solar cells.
Accordingly, there is a need for a low cost high efficiency way of transferring wafers during the fabrication of solar cells.